This invention relates to a shock-absorbing device mounted between a vibration source member and a member to be set into vibration, and a recording/playbacK apparatus for a disc-shaped recording medium employing such shock-absorbing device.
Recently, as the disc-shaped recording media, read-only optical recording media, commonly termed CD-ROM, re-recordable optical recording media and magneto-optical recording media, which may be re-recorded by light or magnetic field modulation, have been proposed. Currently, the CD-ROM and magneto-optical recording media have been put to practical application.
By way of an example, reference is had to the CD-ROM, referred to herein as an optical disc. As a playback apparatus for this optical disc, the following arrangement, which may be reduced in size and may be adapted to various loading systems, represented by a caddie system, a tray system or a top-up system, subject to simple design change, has been proposed.
Referring to FIG. 1, the arrangement comprises a driving unit 206, made up of a spindle motor 202 for rotationally driving an optical disc, not shown, loaded on a turntable 201, an object lens 203 movable radially of the optical disc and adapted for reproducing information signals from the disc by means of a light beam and for converging the light beam, and an optical pickup unit 204 mounting the object lens 203 for movement in a direction away from and towards the optical disc. These elements 202 to 204 are housed within a chassis 205 which in turn is housed within a casing 207 of a main body of the reproducing apparatus, as shown in FIG. 2.
The driving unit 206 is mounted within the casing 207 via a damper 208 mounted on the lateral side of the chassis 205 of the driving unit 206. As shown in FIG. 1A, the damper 208 comprises a cylindrical-shaped thin-walled rubber member 209 having a constricted mid portion 210 with rounded upper and lower portions.
For mounting the damper 208 on the chassis 205, the damper 208 is thrust into a hole 212 surrounded by a hook-shaped protrusion 211 formed on the lateral side of the chassis 205 so that the frame portion of the protrusion 211 is engaged with the constricted portion 210 of the damper 208. A set screw 213 is threaded into a tapped hole 214 in the damper 208 from below the damper 208 into threaded engagement with a driving unit attachment plate 215 of the casing 207 for mounting the driving unit 206 in position within the casing 207.
If vibrations or shocks are exerted for some reason on the casing 207 of the reproducing apparatus, energies proper to these vibrations or shocks from the casing 207 are absorbed in the form of shear deformation or compression deformation of the damper 208 itself for reducing the vibrations or shocks transmitted to the driving unit 206.
However, if, under the demand raised by the user, the mounting state of the casing 207, for example, is changed, as when the mounting state of the casing 207 is to be changed from a horizontal position to a vertical position, or when the playback apparatus is adapted as a car-laden device, larger vibrations or shock are exerted on the casing 207.
However, with the above damper 208, since the vibrations or shocks exerted on the casing 207 are absorbed in the form of the deformation, such as shear deformation or compression deformation, of the damper 208 itself, a certain limitation is imposed on the amount of absorption of the damper 208. Consequently, the larger vibrations or shocks produced under the above situation cannot be absorbed satisfactorily. In such case, the result is that the vibrations or shocks are transmitted from the casing 207 to the driving unit 206 to interfere with control of radial movement of the optical disc in the optical pickup unit 204, that is tracking servo control, or focusing servo control of the object lens 203, so that it becomes impossible to reproduce the information from the optical disc reliably.
It may be contemplated to provide a tension spring between the corner of the driving unit 206 and the casing 207 in place of the damper 208 to insulate transmission of the vibrations and shocks from casing 207. However, if the casing 207 is mounted in a vertically directed orientation, that is if the casing 207 is mounted with the optical disc surface parallel to the perpendicular direction, the driving unit 206 tends to be displaced downwards within the casing 207 under the force of gravity. Consequently, if the playback apparatus has a loading unit of the cartridge insertion type caddie system, the cartridge inserting opening in the casing 207 is displaced relative to the driving unit 206, so that the optical disc accommodated within the cartridge main body cannot be loaded on the turntable 201 of the spindle motor 202 in the driving unit 206.